Talk about taking things in stride. Three scientists stand at a ship’s railing, arms on each others’ shoulders, sun on their faces and a calm blue sea behind them. They look like tourists on a cruise. Nothing in their calm expressions suggests that they have just pulled half a mile of rock out of the Earth. Or that the rock will help them to answer questions about how the planet’s tectonic plates move or about how microbes mingle with heat, water and pressure deep underground.

Oregon State University Professor Anthony Koppers and Toshitsugu Yamazaki of the Geological Society of Japan were co-leaders of the latest cruise conducted under the auspices of the International Ocean Drilling Program (IODP). Their target: the Louisville Seamount Trail — a 2,600-mile-long line of underwater mountains in the South Pacific — where they hoped to learn more about the geophysical processes that produce such features as the Hawaiian Islands or the stretch of ancient volcanoes between the Oregon Cascades and Yellowstone National Park.

Koppers co-edited a special March 2010 issue of the journal Oceanography focusing on seamount science.

According to an IODP news release, the scientific team on the research vessel, JOIDES Resolution, returned to Auckland, New Zealand on February 15 with 806 meters of rock pulled from the seamounts. “During this expedition, we sampled many ancient individual lava flows and a fossilized algal reef. These samples will be used to study the construction and evolution of the individual Louisville volcanoes,” said Koppers.

Night view of the JOIDES Resolution docked in Auckland, New Zealand before its departure on 13 December 2010. (Credit D. Buchs, Australian National University)

Added Yamazaki: “The sample recovery during this expedition was truly exceptional. I believe we broke the recovery record for drilling igneous rock with a rotary core barrel.” A rotary core barrel is a type of drilling tool used for penetrating hard rocks.

The samples were recovered from six sites at five seamounts varying in age from 50 to 80 million years old.

Linear trails of volcanoes found in the middle of tectonic plates, such as the Hawaii-Emperor and Louisville Seamount Trails, are believed to form from a hotspot – a plume of hot material found deep within the Earth that supplies a steady stream of heated rock from depths as great as 2,900 km up to the surface. As the tectonic plate drifts over the hotspot, new volcanoes are formed – and old ones become extinct. Over time, a linear trail of these aging volcanoes is formed.

“Submarine volcanic trails like the Louisville Seamount Trail are unique because they record the direction and speed at which tectonic plates move,” explained Koppers.

Scientists use these volcanoes to study the motion of tectonic plates, comparing the ages of the volcanoes against their location over time to calculate the rate at which the plate moved over a hotspot. These calculations assume the hotspot stays in the same place over time.

Shipboard technicians help carry a core of rock recovered from ancient volcanoes in the Louisville Seamount Trail. (Credit IODP-USIO)

“The challenge,” said Koppers, “is that no one knows if hotspots are truly stationary – or if they somehow wander over time. If they wander, then our calculations of plate direction and speed need to be re-evaluated.”

“But even more importantly,” he continued, “the results of this expedition will give us a more accurate picture of the dynamic nature of the interior of the Earth on a planetary scale.”

Recent studies in Hawaii have shown that the Hawaii hotspot may have moved as much as 15° latitude (about 1,600 kilometers or 1,000 miles) over a period of 30 million years.

“We want to know if the Louisville hotspot moved at the same time and in the same direction as the Hawaiian hotspot – our models suggest that it’s the opposite, but we won’t really know until we analyze the samples from this expedition,” explained Yamazaki.

In addition to the volcanic rock, scientists on this expedition also recovered sedimentary rocks that preserve shells and an ancient algal reef – typical of living conditions in a very shallow marine environment. These ancient materials show that the Louisville seamounts were once an archipelago of volcanic islands.

According to Koppers, “we were really surprised to find only a thin layer of sediments on the tops of the seamounts and only very few indications for the eruption of lava flows above sea level. It seems that the volcanoes have only been at or above the surface of the ocean for a short amount of time – we weren’t expecting this.”

Researchers hailing from all corners of the globe work together to take small samples from the Louisville Seamount Trail cores. These samples will be analyzed to determine the age, composition, and physical properties of the rocks. (Credit IODP-USIO)

The IODP Louisville Seamount Trail Expedition wasn’t solely focused on geology. More than 60 samples from five seamounts were collected for microbiology research, making the Louisville samples the largest collection of volcanic basement rock ever collected for microbiology research during forty years of scientific ocean drilling expeditions.

Exploration of microbial communities within the seafloor, known as the “subseafloor biosphere” is a rapidly developing field of research. Using the Louisville samples, microbiologists will study both living and relict microbial residents within the old sub-seafloor volcanic rocks from Louisville. They will examine population differences in the volcanic rock and overlying sediments and different kinds of lava flows. They will also look for population patterns relative to depth in the seafloor and between seamounts of varying ages.

Over the coming year, samples recovered during the IODP Louisville Seamount Trail expedition will be analyzed to determine their age, composition, and magnetic properties. Like a puzzle, this information will be pieced together to create a story of the eruption history of the Louisville volcanoes, which will be compared to that of the Hawaiian volcanoes to determine whether or not hotspots remain stationary over time.

About IODP

The Integrated Ocean Drilling Program (IODP) is an international research program dedicated to advancing scientific understanding of the Earth through drilling, coring, and monitoring the subseafloor. The JOIDES Resolution is a scientific research vessel managed by the U.S. Implementing Organization of IODP (USIO). Together, Texas A&M University, Lamont-Doherty Earth Observatory of Columbia University, and the Consortium for Ocean Leadership comprise the USIO. IODP is supported by two lead agencies: the U.S. National Science Foundation (NSF) and Japan’s Ministry of Education, Culture, Sports, Science, and Technology. Additional program support comes from the European Consortium for Ocean Research Drilling (ECORD), the Australian-New Zealand IODP Consortium (ANZIC), India’s Ministry of Earth Sciences, the People’s Republic of China (Ministry of Science and Technology), and the Korea Institute of Geoscience and Mineral Resources.